bitmap_to_binary

Converts Bitmap values to a Binary string.

bitmap_to_binary is mainly used for exporting Bitmap data. The compression effect is better than bitmap_to_base64.

If you plan to export data directly to a binary file such as Parquet, this function is recommended.

This function is supported from v3.0.

Syntax

VARBINARY bitmap_to_binary(BITMAP bitmap)

Parameters

bitmap: the Bitmap to convert, required. If the input value is invalid, an error is returned.

Return value

Returns a value of the VARBINARY type.

Examples

Example 1: Use this function with other bitmap functions.

mysql> select hex(bitmap_to_binary(bitmap_from_string("0, 1, 2, 3")));
+---------------------------------------------------------+
| hex(bitmap_to_binary(bitmap_from_string('0, 1, 2, 3'))) |
+---------------------------------------------------------+
| 023A3000000100000000000300100000000000010002000300      |
+---------------------------------------------------------+
1 row in set (0.01 sec)

mysql> select hex(bitmap_to_binary(to_bitmap(1)));
+-------------------------------------+
| hex(bitmap_to_binary(to_bitmap(1))) |
+-------------------------------------+
| 0101000000                          |
+-------------------------------------+
1 row in set (0.01 sec)

mysql> select hex(bitmap_to_binary(bitmap_empty()));
+---------------------------------------+
| hex(bitmap_to_binary(bitmap_empty())) |
+---------------------------------------+
| 00                                    |
+---------------------------------------+
1 row in set (0.01 sec)

Example 2: Convert each value in a BITMAP column into a binary string.

1. Create an Aggregate table page_uv where the AGGREGATE KEY is (page_id, visit_date). This table contains a BITMAP column visit_users whose values are to be aggregated.

       CREATE TABLE `page_uv`
       (`page_id` INT NOT NULL,
       `visit_date` datetime NOT NULL,
       `visit_users` BITMAP BITMAP_UNION NOT NULL
       ) ENGINE=OLAP
       AGGREGATE KEY(`page_id`, `visit_date`)
       DISTRIBUTED BY HASH(`page_id`)
       PROPERTIES (
       "replication_num" = "3",
       "storage_format" = "DEFAULT"
       );

2. Insert data into this table.

     insert into page_uv values
     (1, '2020-06-23 01:30:30', to_bitmap(13)),
     (1, '2020-06-23 01:30:30', to_bitmap(23)),
     (1, '2020-06-23 01:30:30', to_bitmap(33)),
     (1, '2020-06-23 02:30:30', to_bitmap(13)),
     (2, '2020-06-23 01:30:30', to_bitmap(23));
     
     select * from page_uv order by page_id;
     +---------+---------------------+-------------+
     | page_id | visit_date          | visit_users |
     +---------+---------------------+-------------+
     |       1 | 2020-06-23 01:30:30 | NULL        |
     |       1 | 2020-06-23 02:30:30 | NULL        |
     |       2 | 2020-06-23 01:30:30 | NULL        |
     +---------+---------------------+-------------+

3. Convert each value in the visit_users column into a binary-encoded string.

      mysql> select page_id, hex(bitmap_to_binary(visit_users)) from page_uv;
      +---------+------------------------------------------------------------+
      | page_id | hex(bitmap_to_binary(visit_users))                         |
      +---------+------------------------------------------------------------+
      |       1 | 0A030000000D0000000000000017000000000000002100000000000000 |
      |       1 | 010D000000                                                 |
      |       2 | 0117000000                                                 |
      +---------+------------------------------------------------------------+
      3 rows in set (0.01 sec)